GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content: text, mathematics, graphics, interactive content. TeXmacs can also be used as an interface to many external systems for computer algebra, numerical analysis, and statistics. New presentation styles can be written by the user and new features can be added to the editor using Scheme.
Racket (formerly PLT Scheme) is a programming language suitable for implementation tasks ranging from scripting to application development, including GUIs, Web services, etc. It includes the DrRacket programming environment, a virtual machine with a just-in-time compiler, tools for creating stand-alone executables, the Racket Web server, extensive libraries, documentation for both beginners and experts, and more. It supports the creation of new programming languages through a rich, expressive syntax system. Example languages include Typed Racket, ACL2, FrTime, and Lazy Racket.
Diakonos is a customizable, usable console-based text editor. It features arbitrary language scripting, an interactive help system, bookmarking, regular expression searching, parsed ("smart") indentation, macro recording and playback, a multi-element clipboard, multi-level undo, a customizable status line, completely customizable keyboard mapping, and customizable syntax highlighting.
se is a screen-oriented version of the classic UNIX text editor ed. The editor implements many of the commands of ed, but instead of being line-oriented, se is screen-oriented. The command syntax is very familiar to users who already know ed. If you get stuck, there is a built-in help system that describes many of the available commands. Many configurable options can be loaded from a .serc file. se can be run interactively or in a script via the included scriptse utility. The editor is portable across many platforms, supporting major Linux and BSD distributions as well as other systems like GNU, Minix, Haiku, OpenSolaris, and Cygwin.
The aim of LucED is to be a fast and responsive X11 text editor with a simple but powerful user interface similar to NEdit. It uses Lua as an embedded scripting language, and features syntax highlighting that is configurable via PCRE regular expressions with arbitrarily nested patterns.
Evergreen is a cross-platform development environment that tries to be lightweight and language-agnostic yet functional. It started as a project to reimplement Rob Pike's Acme editor for Plan 9 in Java, but has since evolved in directions that help it deal with large codebases and multiple projects/branches at once. Remaining similarities include the tiled windows and the Unix-like reliance on external programs rather than reinventing every wheel. The major philosophical differences include strong support for keyboard-based editing, language-specific functionality, and native platform UI conventions. There are also two new guiding principles: accepting regular expressions and output diffs.